Derivatives, including potential metabolites, of a number of polcyclic aromatic hydrocarbons and aza-polycyclic aromatic hydrocarbons are being synthesized. The relative mutagenicity toward bacterial and mammalian cells and the relative tumorigenicity of the derivatives will be determined in order to assess the structure-activity relationships involved in these biological activities of the molecules. Derivatives of benzo(a)pyrene, dibenzo(a,i)-(a,h)pyrene, and benz(c)acridine are being studied.